Three-phase core



April 22, 1952 B. B. ELLIS EIAL THREE-PHASE CORE 2 SHEETSSHEET 2 FiledJuly 9, 1949 Fig. 8. r

Fig. 7.

s R O T N E V m Belvin B. Ellis, Clifford C. Horsrmon 8 Charles EBurkhordl WITNESSES:

Patented Apr. 22, 1952 THREE-PHASE CORE Belvin B. Ellis, Sharon, and

and Charles E. Burkhardt, signors to Westinghouse East Pittsburgh, Pa.,a

sylvania Clifford C. Horstman Sharpsville, Pa., as- ElectricCorporation,

corporation of Penn Application July 9, 1949, Serial No. 103,863

2 Claims. (Cl. 175356) This invention relates to three-phase corestructures;

Heretofore, Y and T-core structures have been produced having low soundlevel characteristics and satisfactory magnetic values. Numerous jointstructures have been developed in attempts to lower the magnetic lossesbut such joint structures, particularly in the yoke area, have notenabled the reduction of magnetic losses to a value approaching thelosses of the magnetic material without joints therein.

An object of this invention is the production or three-phase corestructures having excellent sound level characteristics and low magneticlosses.

Another object of this invention is to provide a three-phase corestructure having inserts of magnetic materials in the yoke areas thereoffor increasing the amount of magnetic material in the yoke joint areatothereby effect a reduction in the induction at the joints.

A further object of this invention is to provide inserts of magneticmaterial alternately with the laminations of a three-phase corestructure in the yoke area thereof to substantially double the amount ofmagnetic material in the yoke joint area over that in any one of thewinding legs of the core structure;

Other objects of this invention will become apparent from the followingdescription when taken in conjunction with the accompanying drawings, inwhich:

Figure 1 is a view in perspective of a threephase Y-core structureembodying the teachings of this invention;

Figs. 2, 3, 4 and 5 are plan views of the assembly of successivelayers'of laminations in the yoke area of'the core structure of Fig. 1;

Fig. 6 is a view in perspective of a three-phase T-core structureembodying the teachings of this invention; and

Figs. 7, 8 and 9 are plan view of the assembly of successive layers oflaminations in the yoke area of the core structure of Fig. 6.

Referring to Figure 1 of the drawings, this invention is illustrated byreference to a threephase Y-core structure l0 formed of bundles l2, I4and I6 of laminations of magnetic material, the magnetic material beingpreferably silicon iron alloy strip material processed to have apreferred orientation of the grain structure in the direction of thestrips or laminations. Each bundle I2, I 4 and I6 is similarly formed,being bent flatwise of the laminations so that when assembled in nestedrelation the bundles are provided with winding legs [8, 20 and 22,respectively, and turned end portions 24-46, 28-30 and 32- 34,respectively.

Each of the winding legs I3, 23 and 22 is provided with offset joints 36and 38 in the alternate laminations thereof to facilitate separation ofthe upper core section from the lower core section when the windings(not shown) are to be positioned in assembled relation with the Windinglegs. Each of the bundles l2, l4 and iii is provided with the samenumber of laminations so that corresponding laminations of the endportions will form a layer in the'yoke area.

As illustrated more clearly in Figs. 2, 3 and 4, one of the end portionsof each layer of laminations is cut or otherwise formed to have apointed end 39, the edges of the pointed end being cut at angles of 30to the direction of the lamination to provide a pointed end. Thus inFig. 2, the end portion 32 is provided with the pointed end 39, whereasend portions 24 and 28 are provided with square out edges at an angle ofto the direction of thelaminations to butt against the cut edges of thepointed end 39 of end portion 32. The end portions 24, 28 and 32 thusextend outwardly from the yoke joint area thus formed at angles of fromeach other to provide a symmetrical pattern for the core structure.

The second layer of end portion laminations is similarly formed exceptthat the end portion lamination having the pointed end 39 is disposed120 away from the pointed end lamination of the first or external layer.Thus, as shown in Fig. 3, the end portion lamination 24 of the secondlayer is provided with the pointed end 39 for cooperating with thesquare cut ends of the end portion laminations of the second layer ofend portions 28 and 32 to provide a symmetrical yoke area.

Similarly, the third layer of end portion laminations is formed of twosquare cut end portions 24 and 32, the third end portion lamination 28being provided with the pointed end 39 for butting against the squareout edges of end portions 24 and 32. Thus, in the third layerillustrated in Fig. 4, the pointed end portion 28 is disposed 120 fromthe pointed end portions of the first and second layer of end portionlaminations.

Where the bundles l2, l4 and I6 are thus formed with certain of the endportion laminations having pointed ends and being offset relative toadjacent end portion laminations so that when assembled the layers ofthe end portion laminations are successively formed of yoke areas shownin Figs. 2, 3 and 4 repeated a required number of times, it is seen thatthe pointed end 39 of one of the end portion laminations of each layeroverlaps one of the butt joints between two of the end portionlaminations of adjacent layers.

In order to introduce more magnetic material in theyoke core area todecrease the induction at the joint area, an insert 40 of magneticmaterial, preferably silicon iron alloy strip material, is positionedbetween adjacent layers of the end portion laminations in interleavedrelation therewith to overlap the joints formed in each of the adjacentlayers. The inserts 40 preferably have a thickness equal to that of thelaminations forming bundles l2, l4 and 16 so that when assembled withrespect to the joints between the laminations of the cooperative endportions 242B32 and 26--30--34, each of the yoke areas thus formed has aheight substantially equivalent to twice the thickness of a winding legof one of the bundles l2, M or I6.

In practice, the inserts 40 for the Y-core structure ID are formed intothe shape of an equilateral triangle as illustrated in Figs. 1 and 5,the triangular inserts 40, being so cut from magnetic strip materialhaving a preferred grain orientation that the preferred direction is ina direction perpendicular to one of the sides of the triangle and thatthe inserts are of a size to overlap the joints. In assembling theinserts 40, each successive insert is progressively turned or displaced120 from the preceding insert so that the magnetic directions of thesuccessive inserts are symmetrically oriented to give good magneticproperties in three directions disposed 120 with respect to each otherthroughout the height of the yoke area. Thus the grain orientation ofeach of the inserts 40 is in the same direction as the grain orientationof one of the end portion laminations of the two adjacent layers betweenwhich the insert is disposed, the pointed ends 39 of the end portionlaminations of the two layers being disposed 120 apart. Such structuregives an efiicient overlap joint structure resulting in a loweredinduction with a resulting reduction in iron loss.

This invention may also be applied to T-core structures as illustratedin Figs. 6, 7, 8 and 9. In this embodiment, two of the bundles 42 and 44of the flatwise bent and nested laminations formed as described inconnection with the Y- core of Fig. 1 to have winding legs 46 and endportions 5052 and 54-56, respectively, have alternate end portionlaminations offset relative to each other, as shown in Figs. 7 and 8,and are disposed in a vertical plane taken through the winding legsthereof with the end portions 50 and 52 facing the end portions 54 and56, respectively. A third bundle 58 having a winding leg 60 and endportions 62 and 64 is disposed perpendicular to the other two bundles,the end portions 62 and 64 of bundle 53 being formed of laminationswhich are alternately cut at the ends thereof at 45 to the direction ofthe laminations so that the adjacent laminations thereof have pointedends 63 and 65 which are offset relative to each other.

Thus referring to Fig. '7, the external lamination of end portion 50 issquare cut whereas the external lamination of end portion 54 is cut atan angle of 45 to the direction of the lamination, whereby the cut edgeforming pointed end 63 of the external lamination of end portion 62 willcooperate therewith to form a closed butt joint yoke area layer.

The second layer of the end portion laminations is illustrated in Fig.8, the lamination of end portion 54 in this instance being square cutacross its end whereas the end of the lamination of end portion 50 iscut at an angle of 45 to the direction of the lamination. In this layer,the cut of the end of the lamination of end portion 62 is reversed tothe cut of the first layer whereby the pointed end 65 of the secondlamination of the end portion 62 cooperates with the second laminationof each of end portions 50 and 54 to form a closed butt joint yoke arealayer, the joints of which are in overlapped relation with the buttjoints of the first layer of the yoke area as illustrated in Fig. 9.

In the embodiment illustrated in Figs. 6 and 9, square cut inserts 66are disposed between adjacent layers of the laminations of the end por--tions in the yoke areas, the inserts being of a size to overlap the buttjoints in such yoke areas. The inserts 66 are formed of oriented siliconiron sheet, the direction of orientation preferably be ing in thedirection of the aligned end portions of bundles 42 and 44 whereby twoof the laminations of adjacent layers will have an orientation in thesame direction as the orientation of the inserts. However, wheredesired, the alternate inserts 66 may be turned so that the orientationof every second insert is aligned with the grain orientation of thelaminations of end portion 62.

When assembled with the inserts 66 disposed in the yoke area betweenadjacent laminations of the end portions of bundles 42, 44 and 58, thecommon yoke areas have a height or thickness substantially equivalent totwice the thickness of one of the winding legs of the bundles 42, 44 and58. The bundles 42, 44 and 58 are maintained in assembled relation bymeans of steel bands 68 and 10 which extend about the winding legs andend portions of the assembled bundles, the bands crossing at the yokecore areas and being held in position by coupling members 12 in awellknown manner.

This invention makes possible the construction of Y and T-corestructures which have excellent sound level characteristics togetherwith 7 low magnetic losses. The addition of the inserts having apreferred orientation interleaved between the adjacent layers of endportion laminations as described hereinbefore permits the flux producedin such core structures when used as transformer cores, to flow or passthrough the critical yoke joints formed in the common yoke areas at alower flux density thereby keeping the iron loss of the core at a valuemore nearly that value found in testing overlap Epstein samples of themagnetic material. The increase in the magnetic material in the yokejoint area and the overlap joints thereby formed effectively lowers theinduction at the joint correspondingly and the losses decreased inaccordance with the lower induction.

While reference has been made herein to lami tive in that they are shownrelatively thicker than would normally be used in practice in order toclearly illustrate this invention.

We claim as our invention:

1. A three-phase magnetic core comprising, three generally U-shapedbundles of laminations of magnetic strip material having a preferredgrain orientation in the direction of the laminations and bent flatwiseof the laminations to form a winding leg and turned end portions foreach of the bundles, the corresponding end portions of the bundleshaving the ends of certain of the laminations thereof offset withrespect to the others and shaped whereby the ends fit together to formbutt and lap joints in adjacent layers with the end portions positionedto form common Y-shaped yoke areas, and inserts of magnetic sheetmaterial disposed between adjacent layers of the corresponding endportion laminations to overlap the butt joints of the correspondingadjacent layers in the common yoke areas, the inserts having a preferredgrain orientation to provide a most favorable magnetic directiontherein, the inserts between the successive ad jaoent layers of thelaminations being progressively turned 120 apart in assembled relationwith the layers of laminations whereby the most favorable magneticdirection of the inserts between the successive adjacent layers oflaminations is progressively rotated 120, the inserts between theadjacent layers of the laminations being of substantially the samethickness as that of each of the end portion laminations to give each ofthe common yoke areas a height substantially equivalent to twice thethickness of the winding leg of one of the individual bundles.

2. A three-phase magnetic core comprising, three generally U-shapedbundles of laminations of magnetic strip material having a preferredgrain orientation in the direction of the laminations and bent fiatwiseof the laminations to form a winding leg and turned end portions foreach of the bundles, corresponding layers of the corresponding endportion laminations of the three bundles having their ends cut to fittogether in butt joint relation with each other in common yoke areas,and inserts of magnetic sheet material disposed between adjacent layersof the corresponding end portion laminations to overlap the butt jointsof the corresponding adjacent layers in the common yoke areas, theinserts having a preferred grain orientation to provide a most favorablemagnetic direction therein, the inserts between the successive adjacentlayers of the laminations being progressively turned apart in assembledrelation with the layers of laminations whereby the most favorablemagnetic direction of the inserts between the successive adjacent layersof laminations is progressively rotated 120, the inserts being ofsubstantially the same thickness as that of each of the end portionlaminations to give each of the common yoke areas a height substantiallyequivalent to twice the thickness of the winding leg of one of theindividual bundles.

BELVIN B. ELLIS. CLIFFORD C. HORSTMAN. CHARLES E. BURKHARDT.

REFERENCES CITED The following references are of record in the file ofthis patent:

108,862 Austria Feb. 10, 1928

